Multi-directional gearbox deflection limiter for a gas turbine engine

ABSTRACT

A gas turbine engine including a fan, a core including at least one rotatable shaft, and a gearbox mechanically coupling at least one rotatable shaft of the core to the fan is provided. The gas turbine engine also includes a coupling system for mounting the gearbox within the gas turbine engine. The coupling system includes a flexible coupling connected to at least one of a fan frame or a core frame, as well as a torque frame connected to the flexible coupling and the gearbox. Moreover, a deflection limiter is provided, loosely attaching the flexible coupling to the gearbox to provide a predetermined axial range of motion, radial range of motion, and circumferential range of motion between the gearbox and the frame to which the flexible coupling is attached.

FIELD OF THE INVENTION

The present subject matter relates generally to a gas turbine engine, ormore particularly to a coupling system for a gearbox of a gas turbineengine

BACKGROUND OF THE INVENTION

A gas turbine engine generally includes a fan and a core arranged inflow communication with one another. Additionally, the core of the gasturbine engine general includes, in serial flow order, a compressorsection, a combustion section, a turbine section, and an exhaustsection. In operation, air is provided from the fan to an inlet of thecompressor section where one or more axial compressors progressivelycompress the air until it reaches the combustion section. Fuel is mixedwith the compressed air and burned within the combustion section toprovide combustion gases. The combustion gases are routed from thecombustion section to the turbine section. The flow of combustion gassesthrough the turbine section drives the turbine section and is thenrouted through the exhaust section, e.g., to atmosphere. Additionally,the core generally includes one or more shafts extending between theturbine section and the compressor section such that rotation of theturbine section additionally drives the compressor section.

The one or more shafts of the core can also be mechanically coupled tothe fan to facilitate rotation of the fan during operation of the gasturbine engine. However, in order to step down the rotational speed ofthe one or more shafts of the core to a more efficient rotational fanspeed, a gearbox can be provided to mechanically couple the one or moreshafts of the core to a fan shaft driving the fan.

The gearbox may be mounted to one or more frame members using aplurality of support structures. The support structures typically allowfor some movement to accommodate, e.g., vibrations within the fan and/orcore. However, extreme events, such as a bird strike or fan blade lossmay encourage substantial movement of, e.g., the fan shaft along anaxial direction, a radial direction, and/or a circumferential directionof the gas turbine engine. These extreme events may displace the gearboxpast an allowable range, which may cause one or more gears within thegearbox to bind up or otherwise fail.

Accordingly, a mounting assembly for a gearbox capable of accommodatinga certain amount of displacement along the axial direction, the radialdirection, and the circumferential direction of the gas turbine enginewhile limiting such displacement past an allowable range during extremeevents would be useful.

BRIEF DESCRIPTION OF THE INVENTION

Aspects and advantages of the invention will be set forth in part in thefollowing description, or may be obvious from the description, or may belearned through practice of the invention.

In one exemplary embodiment of the present disclosure, a gas turbineengine is provided defining an axial direction, a radial direction, anda circumferential direction. The gas turbine engine includes a fanincluding a fan frame, and a core including a core frame and one or morerotatable shafts. The gas turbine engine also includes a gearboxmechanically connecting one of the one or more shafts of the core to thefan, and a coupling system for mounting the gearbox within the gasturbine engine. The coupling system includes a flexible couplingconnected to at least one of the fan frame or the core frame, and atorque frame connected to the flexible coupling and the gearbox. Thecoupling system also includes a deflection limiter loosely attaching theflexible coupling to the gearbox, the deflection limiter providing foran axial range of motion, a radial range of motion, and acircumferential range of motion between the gearbox and the frame towhich the flexible coupling is attached.

In another exemplary embodiment of the present disclosure, a gear trainfor a gas turbine engine defining an axial direction, a radialdirection, and a circumferential direction is provided. The gear trainincludes a sun gear rotatable by a shaft of the gas turbine engine, aring gear attachable to a ring gear shaft, and a plurality ofintermediate gears rotatably mounted in a gear carrier and meshing withthe sun gear and ring gear. The gear train also includes a couplingsystem. The coupling system includes a flexible coupling for connectionwith a nonrotating component of the gas turbine engine, and a torqueframe connected to the flexible coupling and the gear carrier forconnecting the flexible coupling to the gear carrier. The couplingsystem also includes a deflection limiter loosely attaching the flexiblecoupling to the gear carrier, the deflection limiter providing for anaxial range of motion, a radial range of motion, and a circumferentialrange of motion between the gear carrier and the nonrotating componentto which the flexible coupling is attached.

These and other features, aspects and advantages of the presentinvention will become better understood with reference to the followingdescription and appended claims. The accompanying drawings, which areincorporated in and constitute a part of this specification, illustrateembodiments of the invention and, together with the description, serveto explain the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including thebest mode thereof, directed to one of ordinary skill in the art, is setforth in the specification, which makes reference to the appendedfigures, in which:

FIG. 1 is a schematic cross-sectional view of an exemplary gas turbineengine according to various embodiments of the present subject matter.

FIG. 2 is a cross-sectional view of a gear train of a gearbox inaccordance with an exemplary embodiment of the present disclosure.

FIG. 3 is a close-up, cross-sectional view of the exemplary gearbox ofFIG. 2, mounted within a gas turbine engine.

FIG. 4 is a close-up, cross-sectional view of a coupling system inaccordance with an exemplary embodiment of the present disclosure formounting the exemplary gearbox of FIG. 2 within the gas turbine engine.

FIG. 5 provides a close-up, schematic view of a deflection limiter ofthe exemplary coupling system of FIG. 4.

FIG. 6 provides another close up, cross-sectional view of the deflectionlimiter of the exemplary coupling system of FIG. 4.

FIG. 7 provides a close-up, cross-sectional view of a deflection limiterin accordance with another exemplary embodiment of the presentdisclosure.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to present embodiments of theinvention, one or more examples of which are illustrated in theaccompanying drawings. The detailed description uses numerical andletter designations to refer to features in the drawings. Like orsimilar designations in the drawings and description have been used torefer to like or similar parts of the invention. As used herein, theterms “first”, “second”, and “third” may be used interchangeably todistinguish one component from another and are not intended to signifylocation or importance of the individual components.

Referring now to the drawings, wherein identical numerals indicate thesame elements throughout the figures, FIG. 1 is a schematiccross-sectional view of a gas turbine engine in accordance with anexemplary embodiment of the present disclosure. More particularly, forthe embodiment of FIG. 1, the gas turbine engine is a high-bypassturbofan jet engine 10, referred to herein as “turbofan engine 10.” Asshown in FIG. 1, the turbofan engine 10 defines an axial direction A(extending parallel to a longitudinal centerline 12 provided forreference) and a radial direction R. In general, the turbofan 10includes a fan section 14 and a core turbine engine 16 disposeddownstream from the fan section 14.

The exemplary core turbine engine 16 depicted generally includes asubstantially tubular outer casing 18 that defines an annular inlet 20.The outer casing 18 encases, in serial flow relationship, a compressorsection including a booster or low pressure (LP) compressor 22 and ahigh pressure (HP) compressor 24; a combustion section 26; a turbinesection including a high pressure (HP) turbine 28 and a low pressure(LP) turbine 30; and a jet exhaust nozzle section 32. A high pressure(HP) shaft or spool 34 drivingly connects the HP turbine 28 to the HPcompressor 24. A low pressure (LP) shaft or spool 36 drivingly connectsthe LP turbine 30 to the LP compressor 22.

For the embodiment depicted, the fan section 14 includes a variablepitch fan 38 having a plurality of fan blades 40 coupled to a disk 42 ina spaced apart manner. As depicted, the fan blades 40 extend outwardlyfrom disk 42 generally along the radial direction R. Each fan blade 40is rotatable relative to the disk 42 about a pitch axis P by virtue ofthe fan blades 40 being operatively coupled to a suitable actuationmember 44 configured to collectively vary the pitch of the fan blades 40in unison. The fan blades 40, disk 42, and actuation member 44 aretogether rotatable about the longitudinal axis 12 by LP shaft 36 acrossa power gear box 46. The power gear box 46 includes a plurality of gearsfor stepping down the rotational speed of the LP shaft 36 to a moreefficient rotational fan speed, and as will be discussed in greaterdetail below, is attached to one or both of a core frame or a fan framethrough one or more coupling systems 47.

Referring still to the exemplary embodiment of FIG. 1, the disk 42 iscovered by rotatable front hub 48 aerodynamically contoured to promotean airflow through the plurality of fan blades 40. Additionally, theexemplary fan section 14 includes an annular fan casing or outer nacelle50 that circumferentially surrounds the fan 38 and/or at least a portionof the core turbine engine 16. It should be appreciated that the nacelle50 may be configured to be supported relative to the core turbine engine16 by a plurality of circumferentially-spaced outlet guide vanes 52.Moreover, a downstream section 54 of the nacelle 50 may extend over anouter portion of the core turbine engine 16 so as to define a bypassairflow passage 56 therebetween.

During operation of the turbofan engine 10, a volume of air 58 entersthe turbofan 10 through an associated inlet 60 of the nacelle 50 and/orfan section 14. As the volume of air 58 passes across the fan blades 40,a first portion of the air 58 as indicated by arrows 62 is directed orrouted into the bypass airflow passage 56 and a second portion of theair 58 as indicated by arrow 64 is directed or routed into the LPcompressor 22. The ratio between the first portion of air 62 and thesecond portion of air 64 is commonly known as a bypass ratio. Thepressure of the second portion of air 64 is then increased as it isrouted through the high pressure (HP) compressor 24 and into thecombustion section 26, where it is mixed with fuel and burned to providecombustion gases 66.

The combustion gases 66 are routed through the HP turbine 28 where aportion of thermal and/or kinetic energy from the combustion gases 66 isextracted via sequential stages of HP turbine stator vanes 68 that arecoupled to the outer casing 18 and HP turbine rotor blades 70 that arecoupled to the HP shaft or spool 34, thus causing the HP shaft or spool34 to rotate, thereby supporting operation of the HP compressor 24. Thecombustion gases 66 are then routed through the LP turbine 30 where asecond portion of thermal and kinetic energy is extracted from thecombustion gases 66 via sequential stages of LP turbine stator vanes 72that are coupled to the outer casing 18 and LP turbine rotor blades 74that are coupled to the LP shaft or spool 36, thus causing the LP shaftor spool 36 to rotate, thereby supporting operation of the LP compressor22 and/or rotation of the fan 38.

The combustion gases 66 are subsequently routed through the jet exhaustnozzle section 32 of the core turbine engine 16 to provide propulsivethrust. Simultaneously, the pressure of the first portion of air 62 issubstantially increased as the first portion of air 62 is routed throughthe bypass airflow passage 56 before it is exhausted from a fan nozzleexhaust section 76 of the turbofan 10, also providing propulsive thrust.The HP turbine 28, the LP turbine 30, and the jet exhaust nozzle section32 at least partially define a hot gas path 78 for routing thecombustion gases 66 through the core turbine engine 16.

It should be appreciated, however, that the exemplary turbofan engine 10depicted in FIG. 1 is by way of example only, and that in otherexemplary embodiments, the turbofan engine 10 may have any othersuitable configuration.

Referring now to FIG. 2, a front view of a gearbox 100 for a gas turbineengine in accordance with an exemplary embodiment of the presentdisclosure is provided. In at least certain exemplary embodiments, thegearbox 100 of FIG. 2 may be incorporated into the turbofan engine 10 ofFIG. 1 (e.g., configured as the exemplary gear box 46 depicted), andthus the same or similar numbering may refer to the same or similarparts.

For the embodiment of FIG. 2, the gearbox 100 includes a gear train 102for transferring rotational power from an LP shaft 36 to an output shaftor fan shaft 104. More particularly, the gear train 102 generallyincludes a sun gear 106, a ring gear 108, and a plurality ofintermediate gears. For the embodiment depicted, the gear train 102 isconfigured as a star gear train, and thus the intermediate gears areconfigured as star gears 110. The plurality of star gears 110 are spacedgenerally along the circumferential direction C of the turbofan engine10.

The sun gear 106 is fixed to an input shaft 112, which as will bediscussed below may be attached to the LP shaft 36 of the turbofanengine 10. The ring gear 108 is concentrically disposed about the sungear 106 and is fixed to the fan shaft 104 of the turbofan engine 10.The star gears 110 are positioned between the sun gear 106 and ring gear108 and mesh with the sun gear 106 and ring gear 108. Each of the stargears 110 are mounted on a corresponding bearing 114, which for theembodiment depicted is a journal bearing, to facilitate rotation of therespective star gears 110.

Moreover, a plurality of baffles 116 are positioned between adjacentstar gears 110 and bearings 114. The baffles 116 may be configured aslubrication baffles forming a gearbox lubrication system that provideslubrication to each of the star gears 110 through a main lubricationmanifold (not depicted). Additionally, the baffles 116 may be formedintegrally with, or otherwise fixed to a pair of opposing plates 118located forward and aft of the star gears 110 to form a gear carrier 120(see also FIG. 3, below). The bearings 114 are also attached to the gearcarrier 120. As will be discussed in greater detail below with referenceto FIG. 3, a torque frame 122 (FIG. 3) is provided including extensions124 that connect to the gear carrier 120 through the baffles 116 tomount the gear train 102 and gearbox 100 within the turbofan engine 10.

During operation, the input shaft 112 may provide rotational power fromthe LP shaft 36 to the sun gear 106 to produce rotation of the sun gear106 in a first, clockwise direction, as is indicated by arrow 126. Theindividual star gears 110 may then be rotated about their respectivebearings 114 by the sun gear 106 in a second, counterclockwisedirection, as indicated by arrows 128. Additionally, the ring gear 108may in turn be rotated by the plurality of star gears 110 about theaxial direction A also in the second, counterclockwise direction, asindicated by arrow 130. Due to the intermediate star gears 110, the ringgear 108 and fan shaft 104 rotate about the axial direction A of theturbofan engine 10 at a slower rate than the sun gear 106 and inputshaft 112/LP shaft 36. The fan shaft 104 may then drive the fan 38,rotating a plurality of fan blades 40 and providing thrust for theturbofan engine 10.

It should be appreciated, however, that the exemplary gear train 102depicted in FIG. 2 is provided by way of example only and that in otherexemplary embodiments the gear train 102 may have any other suitableconfiguration. For example, in other exemplary embodiments, the geartrain 102 may include any other suitable number of star gears 110 andmay define any suitable overall gear ratio. Moreover, in still otherexemplary embodiments, the gear train 102 may not be configured as astar gear train, and instead may be configured as a planetary geartrain, wherein the ring gear 108 is stationary the plurality ofintermediate gears are configured as planetary gears. In such anexemplary embodiment, the plurality of planetary gears may rotate aboutroller bearings and also may be attached to, e.g., the fan shaft 104 torotate the fan shaft 104.

Referring now also to FIG. 3, a close-up, cross-sectional view of aforward end of a turbofan engine 10 in accordance with an exemplaryembodiment of the present disclosure is provided having the exemplarygearbox 100 of FIG. 2 mounted therein. As is depicted, the gearbox 100is supported within the turbofan engine 10 by the input shaft 112, thefan shaft 104, and a coupling system 132. The various gears within thegear train 102 of the gearbox 100 are depicted schematically in phantomfor illustrative purposes As will be discussed in greater detail below,the coupling system 132 may permit the gearbox 100 to absorb forcesapplied thereon, e.g., by the fan shaft 104. For example, the couplingsystem 132 may permit the gearbox 100 to absorb vibrations and bendingmoments in a variety of directions applied by the fan shaft 104, whilealso limiting (via a deflection limiter 174, discussed below) movementof the gearbox 100 more than a predetermined amount in any direction.

Specifically, the LP shaft 36 is attached to the input shaft 112 todrive the input shaft 112. The LP shaft 36 is supported within the core16 by a core frame 134 including a strut 136. The strut 136 isconfigured to support the LP shaft 36 via a bearing assembly 138. Forthe embodiment depicted, the bearing assembly 138 includes a single ballbearing assembly, which may accommodate rotation of the LP shaft 36 andsupport the LP shaft 36 along the radial direction R. However, in otherexemplary embodiments, the bearing assembly 138 may additionally, oralternatively, include any other suitable bearing elements, such as oneor more roller element bearings.

The input shaft 112 extends between a first end 140 connected to the LPshaft 36 and a second end 142 connected to the gearbox 100.Specifically, for the embodiment depicted, the second end 142 of theinput shaft 112 is attached to the sun gear 106 for rotating the sungear 106 in the first direction 126. Accordingly, during operation ofthe turbofan engine 10, the LP shaft 36 drives the input shaft 112,which in turn, drives the sun gear 106. The sun gear 106, rotates theplurality of star gears 110, which also rotates the ring gear 108.

As is also depicted, the ring gear 108 is attached to the fan shaft 104,such that rotation of the ring gear 108 correspondingly rotates the fanshaft 104. The fan shaft 104 is supported by a fan frame 144 including afirst fan strut 146 and a second fan strut 148. Specifically, the firstand second fan struts 146, 148 support the fan shaft 104 via arespective pair of fan bearings 150. The respective pair of fan bearings150 are configured to support the fan shaft 104 while accommodatingrotation of the fan shaft 104. For the embodiment depicted, each of thepair of fan bearings 150 are configured as a roller element bearings.However, in other exemplary embodiments, any other suitable type ofbearings and/or bearing configuration may be provided. Additionally, inother exemplary embodiments any other suitable fan frame configurationmay be provided.

During operation of the turbofan engine 10, vibrations and other forceson the fan 38 may be propagated through the fan shaft 104 to the gearbox100. For example, turbulent airflow across the plurality of fan blades40, or a bird strike to the plurality of fan blades 40 may generatestresses and vibrations on the fan shaft 104. In order to accommodatesuch stress and vibration without derailing one or more of the gearswithin the gear train 102 of the gearbox 100, the coupling system 132 isprovided for flexibly attaching the gearbox 100 to at least one of thefan frame 144 or the core frame 134. Particularly for the embodimentdepicted, the coupling system 132 flexibly attaches the gearbox 100 tothe core frame 134 at a location aft of the gearbox 100.

Referring now also to FIG. 4, a close-up view is provided of theexemplary coupling system 132 of FIG. 3. As is depicted, the couplingsystem 132 generally includes a flexible coupling 152 connected to thecore frame 134 at a first end 154 of the flexible coupling 152.Specifically, the first end 154 of the flexible coupling 152 includes amounting flange 156 attached to the strut 136 of the core frame 134 viaa mechanical fastener or bolt 157. Thus, the first end 154 of theflexible coupling 152 is attached to a nonrotating component of theturbofan engine 10 to mechanically ground the coupling system 132depicted. It should be appreciated, however, that in other exemplaryaspects, the flexible coupling 152 may additionally, or alternatively,be attached at any other suitable location within the core frame 134, oralternatively to, e.g., the fan frame 144 at the first end 154.

At a second end 158 of the flexible coupling 152, the flexible coupling152 includes a second mounting flange 160 for attachment to acorresponding mounting flange 162 of the torque frame 122 via anothermechanical fastener or bolt 163. The torque frame 122 is provided toconnect the flexible coupling 152 to the gearbox 100. Specifically, forthe embodiment depicted, the torque frame 122 is attached to the gearcarrier 120 of the gearbox 100, as discussed above with reference toFIG. 2.

Between the first and second ends 154, 158, the flexible coupling 152generally includes a spring-like member 164 that absorbs movementgenerally along the radial direction R, the axial direction A, and thecircumferential direction C (FIG. 2) of the turbofan engine 10.Specifically, the spring-like member 164 of the flexible coupling 152includes a plurality of bends 166 that may increase or decrease itsangle, or change a direction of its angle, in order to accommodatemovement of the gearbox 100 relative to the core frame 134 along theaxial, radial, and circumferential directions A, R, C. The flexiblecoupling 152 may be formed of a single piece of material bent to adesired shape, or alternatively, may be formed of one or more suitablematerials having desired mechanical properties (e.g., strength,ductility, hardness, impact resistance, etc.).

The torque frame 122 member generally includes a body portion 168 and adisk 170, the disk 170 extending between the body portion 168 andmounting flange 162. The body portion 168 and disk 170 of the torqueframe 122 may have a generally annular shape extending along thecircumferential direction C (see FIG. 2) of the turbofan engine 10.Additionally, although not depicted, the torque frame 122 member mayinclude a plurality of the mounting flanges 162 circumferentially spacedfor attachment to correspondingly spaced mounting flanges 160 of theflexible coupling 152. As will be discussed in greater detail below, aportion of the body portion 168 of the torque frame 122 extends outwardalong the radial direction R to form a radially extending tab 172.

During typical operation of the turbofan engine 10, the flexiblecoupling 152 provides sufficient vibration dampening and stability tothe gearbox 100 to prevent one or more gears within the gear train 102of the gearbox 100 from binding or otherwise becoming derailed. However,during an extreme event, forces on gearbox 100 from, e.g., the fan shaft104, may be sufficient to move the gearbox 100 relative to the coreframe 134 an amount that may cause one or more gears within the geartrain 102 of the gearbox 100 to bind. Accordingly, the coupling system132 further includes a deflection limiter 174 loosely attaching theflexible coupling 152 to the gearbox 100 proximate the first end 154 ofthe flexible coupling 152. Specifically, the deflection limiter 174allows for a range of motion along the axial direction A (i.e., an axialrange of motion), a range of motion along the radial direction R (i.e.,a radial range of motion), and a range of motion along thecircumferential direction C (i.e. a circumferential range of motion)between the gearbox 100 and the frame member to which the flexiblecoupling 152 is attached. More specifically, the deflection limiter 174allows for the gearbox 100 to move relative to the core frame 134 alongthe radial direction R, along the axial direction A, and along thecircumferential direction C a predetermined amount that may correspondto a typical amount of movement required to absorb expected vibrationforces on the gearbox 100. However, once the gearbox 100 begins to movepast the allowable ranges of motion, the deflection limiter 174 preventsfurther movement to ensure the gears within the gear train 102 of thegearbox 100 remain meshed and do not bind. Specifically, the deflectionlimiter 174 blocks any movement of the gearbox 100 relative to the coreframe 134 past the axial, radial, and circumferential ranges of motion.

Notably, for the embodiment depicted, the deflection limiter 174 looselyattaches the flexible coupling 152 to the gearbox 100 through the torqueframe 122. However, in other embodiments, the deflection limiter 174 mayinstead loosely attach the flexible coupling 152 directly to the gearbox100, such as directly to the gear carrier 120 of the gearbox 100.

Referring now also to FIGS. 5 and 6, close up, schematic views areprovided of the exemplary deflection limiter 174 of FIG. 4. FIG. 5provides for a close-up, schematic view of the exemplary deflectionlimiter 174 of FIG. 4 along the axial direction A, and FIG. 6 providesfor a close-up, schematic view of the exemplary deflection limiter 174of FIG. 4 along the radial direction R.

As stated, the deflection limiter 174 defines an axial range of motion(FIG. 5), a radial range of motion, and a circumferential range ofmotion (FIG. 6). For the embodiment depicted, the deflection limiter 174includes a pin 176 extending between the flexible coupling 152 and thetorque frame 122. Specifically, the pin 176 includes a head 178 and abody 180, the body 180 defining a distal end 182 opposite the head 178.Additionally, the body 180 of the pin 176 extends through an opening 184defined in the tab 172 of the torque frame 122 and into the flexiblecoupling 152 proximate the first end 154 of the flexible coupling 152.The distal end 182 of the body 180 of the pin 176 may be attached to theflexible coupling 152 in any suitable manner. For example, the distalend 182 of the body 180 of the pin 176 may be rotatably engaged with theflexible coupling 152 via, e.g., corresponding threads. However, inother exemplary embodiments, the distal end 182 may be attached to theflexible coupling 152 in any other suitable manner. For example, inother exemplary embodiments, the distal end 182 of the pin 176 may bepivotally attached to the flexible coupling 152 using a hinge or othersuitable attachment mechanism.

As is also depicted, the deflection limiter 174 includes a bumper 186mounted to the flexible coupling 152. For the embodiment depicted, thebumper 186 is located between the flexible coupling 152 and the torqueframe 122 and is positioned around the body 180 of the pin 176. Thebumper 186 may be formed of, e.g., an elastomeric material, to minimizeany damage to the flexible coupling 152 or the torque frame 122 when thetab 172 of the torque frame 122 contacts the flexible coupling 152.However, in other exemplary embodiments, the deflection limiter 174 maynot include the bumper 186, or may include a bumper 186 formed of anyother suitable material and positioned at any suitable location.

Referring still to FIGS. 5 and 6, the pin 176 defines a gap with atleast one of the flexible coupling 152 or the torque frame 122 along theaxial direction A (i.e., an axial gap, FIG. 5), a gap with at least oneof the flexible coupling 152 or the torque frame 122 along the radialdirection R (i.e., a radial gap, FIGS. 5 and 6), and a gap with at leastone of the flexible coupling 152 or the torque frame 122 along thecircumferential direction C (i.e., a circumferential gap, FIG. 6). Morespecifically, the deflection limiter 174 defines a first axial gap 188between the head 178 of the pin 176 and the tab 172 of the torque frame122 and a second axial gap 190 between the tab 172 of the torque frame122 and the flexible coupling 152. Additionally, the deflection limiter174 defines a first radial gap 192 and a second radial gap 194 betweenopposing sides of the body 180 of the pin 176 and respective portions ofthe tab 172 of the torque frame 122 (i.e., with an edge of the opening184 in the tab 172). Moreover, the deflection limiter 174 defines afirst circumferential gap 196 and a second circumferential gap 198between opposing sides of the body 180 of the pin 176 and respectiveportions of the tab 172 of the torque frame 122 (i.e., with an edge ofthe opening 184 in the tab 172). The axial gaps 188, 190, radial gaps192, 194, and circumferential gaps 196, 198 may define the axial rangeof motion, radial range of motion, and circumferential range of motion,respectively, provided for by the deflection limiter 174.

In at least certain exemplary embodiments, the axial range of motion,radial range of motion, and circumferential range of motion may all besubstantially equal. Alternatively, however in other exemplaryembodiments, one or more of the axial, radial, and circumferentialranges of motion may be greater than the other ranges of motion. By wayof example only, in at least certain exemplary embodiments, one or moreof the axial, radial, and/or circumferential ranges of motion may be atleast about 0.25 inches, at least about 0.5 inches, at least about oneinch, at least about two inches, or at least about three inches. Itshould also be appreciated, that as used herein, terms of approximation,such as “about” or “approximately,” refer to being within a ten percentmargin of error.

It should also be appreciated that in other exemplary embodiments, thedeflection limiter 174 may loosely attach the flexible coupling 152 tothe gearbox 100 in any other suitable manner to define axial, radial,and circumferential ranges of motion. For example, FIG. 7 provides aclose-up, schematic view of a deflection limiter 200 in accordance withanother exemplary embodiment of the present disclosure. The exemplarydeflection limiter 200 depicted in FIG. 7 includes a pair ofcomplementary channels. Specifically, the exemplary deflection limiter200 includes a first channel 202 attached to the flexible coupling 152and a second channel 204 attached to the torque frame 122. The firstchannel 202 includes a first lip 206 defining a first slot 208 and thesecond channel 204 similarly includes a second lip 210 defining a secondslot 212. The first lip 206 of the first channel 202 is positioned inthe second slot 212 of the second channel 204 and the second lip 210 ofthe second channel 204 is positioned in the first slot 208 of the firstchannel 202. The deflection limiter 200 defines axial gaps between thevarious components along the axial direction A to allow for a range ofmotion along the axial direction A. The exemplary deflection limiter 200of FIG. 7 additionally includes a cap 214 extending from the torqueframe 122 and over a base of the second lip 210 of the second channel204. The cap 214 defines a radial gap with the base of the second lip210 of the second channel 204 to allow for a range of motion along theradial direction R. Additionally, although not depicted, one or both ofthe first channel 202 or the second channel 204 may include a tab atopposing ends along the circumferential direction C defining acircumferential gap with an adjacent channel to allow for range ofmotion along the circumferential direction C.

A gas turbine engine including a coupling system in accordance with anexemplary embodiment of the present disclosure may better accommodateextreme forces on a fan of the gas turbine engine. Specifically, a gasturbine engine having a coupling system for attaching a gearbox to aframe member, the coupling system including a deflection limiterproviding for an axial, radial, and circumferential range of motion, maybetter accommodate extreme forces on a fan of the gas turbine engine.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to practice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims, and may include other examplesthat occur to those skilled in the art. Such other examples are intendedto be within the scope of the claims if they include structural elementsthat do not differ from the literal language of the claims, or if theyinclude equivalent structural elements with insubstantial differencesfrom the literal languages of the claims.

What is claimed is:
 1. A gas turbine engine defining an axial direction,a radial direction, and a circumferential direction, the gas turbineengine comprising: a fan including a fan frame; a core including a coreframe and one or more rotatable shafts; a gearbox mechanicallyconnecting one of the one or more shafts of the core to the fan; and acoupling system for mounting the gearbox within the gas turbine engine,the coupling system comprising a flexible coupling connected to at leastone of the fan frame or the core frame; a torque frame connected to theflexible coupling and the gearbox; and a deflection limiter looselyattaching the flexible coupling to the gearbox, the deflection limiterproviding for an axial range of motion, a radial range of motion, and acircumferential range of motion between the gearbox and the frame towhich the flexible coupling is attached.
 2. The gas turbine engine ofclaim 1, wherein the deflection limiter blocks movement of gearbox pastthe axial range of motion, past the radial range of motion, and past thecircumferential range of motion.
 3. The gas turbine engine of claim 1,wherein the deflection limiter includes a pin extending between theflexible coupling and the torque frame.
 4. The gas turbine engine ofclaim 3, wherein the pin defines an axial gap with at least one of theflexible coupling or the torque frame, wherein the pin defines a radialgap with at least one of the flexible coupling or the torque frame, andwherein the pin defines a circumferential gap with at least one of theflexible coupling or the torque frame.
 5. The gas turbine engine ofclaim 3, wherein the pin defines a distal end, and wherein the distalend of the pin is attached to the flexible coupling.
 6. The gas turbineengine of claim 1, wherein the deflection limiter includes a bumpermounted to the flexible coupling.
 7. The gas turbine engine of claim 6,wherein the bumper is formed of an elastomeric material.
 8. The gasturbine engine of claim 1, wherein the deflection limiter looselyattaches the flexible coupling to the gearbox through the torque frame.9. The gas turbine engine of claim 1, wherein the flexible coupling isconnected to the core frame at a first end.
 10. The gas turbine engineof claim 1, wherein the gearbox includes a sun gear, a ring gear, and aplurality of star gears meshing with the sun gear and ring gear, andwherein the plurality of star gears are rotatably mounted within a stargear carrier.
 11. The gas turbine engine of claim 10, wherein the torqueframe is mounted to the star gear carrier.
 12. The gas turbine engine ofclaim 1, wherein the flexible coupling is connected to at least one ofthe fan frame or the core frame at a first end, and wherein thedeflection limiter loosely attaches the torque frame member to theflexible coupling at a location proximate the first end of the flexiblecoupling.
 13. A gear train for a gas turbine engine defining an axialdirection, a radial direction, and a circumferential direction, the geartrain comprising: a sun gear rotatable by a shaft of the gas turbineengine; a ring gear attachable to a ring gear shaft; a plurality ofintermediate gears rotatably mounted in a gear carrier and meshing withthe sun gear and ring gear; and a coupling system comprising a flexiblecoupling for connection with a nonrotating component of the gas turbineengine; a torque frame connected to the flexible coupling and the gearcarrier for connecting the flexible coupling to the gear carrier; and adeflection limiter loosely attaching the flexible coupling to the gearcarrier, the deflection limiter providing for an axial range of motion,a radial range of motion, and a circumferential range of motion betweenthe gear carrier and the nonrotating component to which the flexiblecoupling is attached.
 14. The gear train of claim 13, wherein thedeflection limiter blocks movement of gearbox past the axial range ofmotion, past the radial range of motion, and past the circumferentialrange of motion.
 15. The gear train of claim 13, wherein the deflectionlimiter includes a pin extending between the flexible coupling and thetorque frame.
 16. The gear train of claim 15, wherein the pin defines anaxial gap with at least one of the flexible coupling or the torqueframe, wherein the pin defines a radial gap with at least one of theflexible coupling or the torque frame, and wherein the pin defines acircumferential gap with at least one of the flexible coupling or thetorque frame.
 17. The gear train of claim 13, wherein the deflectionlimiter includes a bumper mounted to the flexible coupling.
 18. The geartrain of claim 13, wherein the deflection limiter loosely attaches theflexible coupling to the gearbox through the torque frame.
 19. The geartrain of claim 13, wherein the flexible coupling is configured forconnection with a nonrotating component of the gas turbine engine at afirst end, and wherein the deflection limiter loosely attaches thetorque frame member to the flexible coupling at a location proximate thefirst end of the flexible coupling.
 20. The gear train of claim 13,wherein the gear train is a star gear train, and wherein the pluralityof intermediate gears are a plurality of star gears.